Previous data input or typewriter terminals have consisted of either a standard typewriter keyboard format, where each key enters a specific character, or a system which involves manipulation of a set of keys through complex data entry schemes which require the operator to memorize pushbutton positions for all letters of the alphabet, punctuation, numbers, and input control functions, such as entering data and shifting from lower case to upper case, and any other specialized symbols. The prior art data entry schemes of the latter system are based upon activating one or more keys in a specific pattern to produce a given character, with most characters requiring the use of several keys simultaneously. One invention which utilizes the data entry scheme system requires the user to manipulate five four-position transducer units, one unit assigned to each of the fingers of the user's hand. The switches in the units move linearly from one position to another, wherein different characters are entered by varying the positions of each of the switches in the transducer units (U.S. Pat. No. 3,022,878 by Seibel). Other devices utilize simple finger-activated unidirectional pushbuttons rather than complex multiposition transducer switches. The pushbuttons are arranged in various configurations, such as key arrangements which include mounting the buttons to a cylindrical handgrip, displaying them in a rectangular array, and positioning an array of five keys on a planar surface with one key designated for each finger. The five-key planar array terminal utilizes a character pushbutton combination system whereby the input keys for most letters of the alphabet correspond to positions on a five-point inverted parabola that roughly conform to the outline of the letter or its interception points when placed on the grid. For example, a "b" has contact points at the apex coordinate and the two-point positions on the right side of the parabola, because the open loop of the letter is located on the right side of the shaft. A "d," on the other hand, would contact the apex and the two points on the left side of the grid (U.S. Pat. No. 3,980,823 by Howard, U.S. Pat. No. 4,442,506 and 4,443,789 by Endfield).
One variation of the previously mentioned data entry scheme locates flex sensors, touch sensors, and tilt sensors on various locations of a glove which fits over the hand. The sensors were activated either individually or in series by flexing certain joints or touching certain areas of the hand, resulting in a given command. The glove was used to input characters using "sign language." However, the glove was problematic, as the sensors were difficult to adjust to eliminate inadvertent activation by flexing, tilting, or touching. Moreover, the uncertainty as to the degree of tilt or flex necessary to input characters presented another drawback to the user of the glove device since the flex and tilt sensors were to be operated by hand movements not normally performed by the user in everyday life (U.S. Pat. No. 4,414,537 by Grimes).
A second embodiment similar to the glove device locates touch sensors on the inner surface of a mold made to conform to the shape of a human hand. A total of eight touch sensors are distributed such that the thumb and heel of the hand contact two switches each, while the remaining fingers each have one switch. As discussed in regard to the other embodiments, the data entry scheme system requires the user to press multiple buttons in combinations.
In summary, the prior art includes character input terminals operated by one hand which force the operator to remember complex pushbutton schemes, most conceived without any logical scheme as to which keys are used for certain characters. Therefore, today the user of such a terminal is faced with the dilemma of either memorizing the data entry schemes or using a simpler system with fewer possible input commands and thus a less powerful system.